Question Paper: Operating Systems : Question Paper Dec 2012 - Electronics & Telecomm. (Semester 6) | Mumbai University (MU)
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## Operating Systems - Dec 2012

### Electronics & Telecomm. (Semester 6)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.
1(b) Compare and contrast short term, long term and medium term scheduling.(10 marks) 2(a) Consider the following set of processes with length of CPU burst given in milliseconds :< br >< table border = 1 style = width : 50 %> < tbody > < tr > < td valign = top > < p > < b >< i > Process < td valign = top > < p > < b >< i > Burst - time < td valign = top > < p > < b >< i > Priority < tr > < td valign = top > < p > < b >< i > P1 < td valign = top > < p > < b >< i > 10 < td valign = top > < p > < b >< i > 3 < tr > < td valign = top > < p > < b >< i > P2 < td valign = top > < p > < b >< i > 1 < td valign = top > < p > < b >< i > 1 < tr > < td valign = top > < p > < b >< i > P3 < td valign = top > < p > < b >< i > 2 < td valign = top > < p > < b >< i > 3 < tr > < td valign = top > < p > < b >< i > P4 < td valign = top > < p > < b >< i > 1 < td valign = top > < p > < b >< i > 4 < tr > < td valign = top > < p > < b >< i > P5 < td valign = top > < p > < b >< i > 5 < td valign = top > < p > < b >< i > 2 < br > The arrival order is P1, P2, P3, P4, P5 all at time 0.< br > i ) Draw Gantt charts illustrating execution of these processes using FCFS, SJF(non - pre - emptive) and RR(quantum = 1) algorithms < br > ii ) Calculate the turnaround time and waiting time for each process and state which algorithm results in minimum waiting time.(12 marks) 2(b) What is mutual exclusion? Describe ways in which it can be achieved.(8 marks) 3(a) Assume that the disk head is initially positioned over track 100.For the disk space request of 27, 129, 110, 186, 147, 41, 10, 64 and 120.Show how disk scheduling is done for i ) SSTF ii ) C - SCAN iii ) C - LOOK.Calculate the average seek length and show the tracing of the requests.(10 marks) 3(b) Discuss different file allocation methods.(10 marks) 4(a) What are different methods of free space management to keep track of free disk space.(10 marks) 4(b) Discuss different approaches of I / O buffering provided by the OS.(10 marks) 5(a) Consider the following sequence of page references : 1, 0, 2, 2, 1, 7, 6, 7, 0, 1, 2, 0, 3, 0, 4, 5, 1, 2.< br > How many page fault would occur for LRU, FIFO and optimal algorithms assuming a page frame of 4? (10 marks) 5(b) Explain necessary and sufficient conditions for a deadlock.Explain how resource allocation graph determines a deadlock.(10 marks) 6(a) What are the characteristics of real - time systems? (10 marks) 6(b) Compare and contrast deadline scheduling and rate monotonic scheduling algorithms.(10 marks)

### Write short notes on (ANY TWO):

7(a) System calls (5 marks) 7(b) Semaphores.(5 marks) 7(c) User threads and Kernel threads.(5 marks) 7(d) Application of RTOS (5 marks) 1(a) What is critical section problem? Discuss Dekkers solution and show how it satisfies all the requirements of critical section problem.(10 marks)